Add possibility of creating beekeeper session with clive

Closes #315

This MR introduces functionality that will allow to create Beekeeper session token by using clive.

clive beekeepeer spawn --create-session

This command requires a runnig Beekeeper instance by using clive beekeeper spawn

Maybe instead of adding flag --create-session we could add something like this:

clive beekeeper spawn instance  - create bk instance
clive beekeeper spawn session BEEKEEPER_ENDPOINT
where:
  BEEKEEPER_ENDPOINT - optional address of bk which will create session token, if no provided, use one provided by `spawn instance`